This disclosure pertains to method for fabricating high quality optical material, such as lenses and fibers, by curing liquid polydimethylsiloxane (PDMS) in or on heated substrates.
Lenses are traditionally constructed with rigid materials such as glass or plastics by mechanical polishing or injection molding. High optical quality lens surface requires well-controlled fabrication parameters which increases complexity and reduces yield. Current demands for complementary metal-oxide semiconductor (CMOS) image sensors have resulted in the increase in fabricating small lenses ranging from 1 mm to 1 cm in diameter. In addition, emerging applications of flexible optoelectronics demand mechanically flexible lens materials. Fluidic lenses in particular is a simple method of creating small lenses of high quality without the requirement of molds or complex parameter control. However, an encapsulated fluidic lens requires a system to provide mechanical stability, and prevent evaporation. In contrast, lens formation due to surface energy minimization during polymer curing has provided an alternative method for making high quality, low-cost “fluidic” lenses that are independent components, flexible and robust.
Polymers have been generally utilized as a lens material by three categories of fabrication techniques: 1) lithographic methods, 2) surface-tension-driven methods, and 3) imprinting or embossing methods. These approaches demonstrate the feasibility of creating lenses with good optical characteristics and reproducibility; however, these techniques involve either time-consuming fabrication procedures typically measured in hours, or have high costs due to lithographic or molding equipment required, and generally limit the size of the lens to the micrometer scale. A recently introduced alternative method of creating a lens by droplet formation requires iterative drop-bake cycles to achieve a desired focal length. What is needed is a method for the production of high quality, inexpensive lenses with optimal focal length that requires minimal steps and is low cost.